Hiya.. I have a tank with betta named Napoleon (its a 20gallon.. i've had a betta for a couple yrs now.. love em).. ANYWAY...
I know he'd be fine with the mollies and frogs... Mine is in with a pleco, tetras, 2 african dwarf froggies, and a catfishy..My previous betta used to be with a molly.

As for the sharks...well they tend to be agressive from what i've seen..they would worry me. My husbands father has some (about 7 inches long now!) and they pick on everyone, but it could just be his fish (he seems to get the mean spirited ones)

Doubt that helped much as for a clear cut answer but I hope it helped out a little teeny bit.